Introduction Although many studies have found that Physical Education (PE) is a popular subject there is an on-going discussion about its aim and what legitimizes it as a school subject. What knowledge appears as legitimate within the subject of PE is, however, hard to identify, which creates controversies within the field. Therefore this study aims to contribute to the discussion by increasing the understanding about what knowledge appears as valid in PE in the perspective to other subjects in Sweden. Theoretical and methodological perspectives The conceptual framework used is curriculum theory, inspired by Bernstein’s (2000) and Lundgren’s (1981) theoretical work on the social construction of knowledge. The focus is on selection processes of knowledge in the educational system. According to Bernstein, education is a field, like any other field, where there is a struggle between interests and actors competing to define the field but also arguing about what knowledge is to be counted as legitimate. In this study I will use different empirical material. The first material comprises applications to the government in 2011 about starting teacher education programmes in Sweden and, further, subject descriptions from six departments of teacher education as well as various policy documents for the subject in the compulsory school. The second material contains interviews with actors who have influence over how the subject is formulated for teacher educations as well as for the compulsory school. As a basis for comparison and analysis, material from four different teacher education and school subjects will be gathered. The subjects include PE, music, English and mathematics. The selection is based on the different traditions that these subjects represent. Expected results The result will contribute with knowledge about similarities and dissimilarities according to what knowledge appears as valid in different subjects and how this is defined. Moreover, the result will provide knowledge about how different subjects relate to the primary field of production and how this relation is expressed in these subjects. The study is most likely to offer an understanding about the identity problem of the subject of PE in the perspective of what knowledge appears as legitimate in relation to other subjects, but also about the character of these different subjects as well as how they relate to the primary field of production. The first part of the study will be implemented during 2014 and the second during 2015.